“Snowpiercer” is a film full of both wonders and horrors, rendered beautifully and hugely. But the most wonderful, horrible thing of all is a small monologue, delivered near the end. I’m going to be thinking about this movie for a long, long time, but more than anything else, that small speech is going to be on my mind. Wow.

The film, the English-language debut of South Korean auteur Bong Joon-ho (best known for “The Host”), is full of thoughts and ideas, not to mention some of the most exhilarating filmmaking in memory. This is a special film, one that begs to be talked about, debated and analyzed.

“Snowpiercer” is yet another film set in a dystopian future, but at least it comes up with a new angle: An attempt to stop global warming by shooting gas into the atmosphere has backfired spectacularly, resulting in a new ice age that’s killed off virtually all life on Earth. The remaining human remnant has been packed onto a train that endlessly circles the globe- and that train has been segregated by social class, with the rich up front and the poor in the back- but revolution is in the air. (How everything else in the world froze but the train tracks didn’t is never quite explained.)

Chris Evans (Captain America himself, never better) is the hero, a guy from the back of the train and leader of the resistance, and he’s joined by his sidekick (Jamie Bell), the film’s Obi-Wan figure (John Hurt), a mother searching the train for her son (Octavia Spencer) and a pair of Koreans (Song Kang-ho and Go Ah-sung) whose powers are the ability to open any door and clairvoyance, respectively. Ewan Bremner also has a memorable turn as a member of the resistance with some seriously funny facial expressions.

The first half hour is a tad underwhelming; it begins to feel like merely a slightly more politically conscious version of the Steven Seagal vehicle “Under Siege” (or maybe “Under Siege 2″- whichever one was on a train and not a submarine.) There are even a couple of brawl sequences that are shot in hacky-seeming shaky cam, which make “Snowpiercer” seem like the by-the-numbers action movie that it very much isn’t.

But it gets much, much better, starting with a bravura acton sequence that focuses on Evans slicing through a train car. As the movie goes on and the characters move further down the train, the visual style keeps changing radically. I don’t want to spoil too much, but a scene with Alison Pill as a manic school teacher was so brilliant that I wish I could’ve rewound it in the theater and watched it again.

And it all leads up to that astonishing monologue which, while not quite so exciting as some of what comes before and after, is so powerful that I feel like it’s what people will most remember about this film. And the film ends exactly the way it should.

As you may have gathered, this is a film that’s quite critical of capitalism, or at the very least critical of the form of capitalism in which there’s extreme inequality, the rich are assholes who flaunt their wealth, and the poor are kept in conditions resembling slavery. What’s undoubtable is that the entire thing is one long rebuke to the Ayn Rand canon, as Rand often used trains as a symbol of the glories of capitalism. “Snowpiercer” does the exact opposite- and even throws in Tilda Swinton as a particularly noxious Rand stand-in.

The acting is first-rate across the board; I had no idea Evans had this sort of subtle work in him. Next spring we’re going to be debating whether or not Pill’s tiny amount of screen time is enough for Oscar consideration or not. And I loved Vlad Ivanov as one of the evil henchmen, who strongly resembles the late character actor J.T. Walsh, and here plays a Walsh-type role. I won’t give away who plays the ultimate villain, but it’s an actor who played a very similar part at the end of a certain ’90s film.

Yes, I’m sick of every other movie I see being set in a post-apocalyptic hellscape too. But “Snowpiercer” is something truly special, so far beyond all the others. This film, released in most of the world last year, has been infamously botched by the Weinstein Company; see Ty Burr’s definitive piece in the Boston Globe for all the unfortunate detail. But it’s starting to earn strong word of mouth, and will debut on video-on-demand this weekend. Please do check it out- and be ready for a whole lot of surprises.